Alright, I'll better throw in my two cents... We humans are arrogant. What makes us think that we have the right to decide whether one should live or die? If it's possible, you should always save a life, if it's for the better of the person. I mean, if the life for that guy/girl would be lying in bed staring at the roof and get feeded three times a day, I would perhaps reconsider.
But just because someone has a certain belief does not give that someone the right to decide that if her/his religion doesn't allow it, then there will be no medical treatment for the sick. I mean, is it sure that the sick would agree? Is it sure that the sick one would later have the same beliefs? No. Then I'd say, the mother/fathers job is to raise their child in order to let them make their own decisions, and not just steal that opportunity from them just because of what they belive. It's immoral. It's just as immoral as when a priest go to war. I mean, there are under no circumstances that a christian has the right to just break the rules of the ten commandments. "Thou shallt not kill". But then again, there are endless of times when priests, bishops and other has encouraged people to go to war and so on. How immoral is that?
I'd say, if you refuse someone medical treatment, then it's the same thing as pulling a trigger and blowing the brains out.
Just for the record, I'm an atheist.